Chemistry: Polar Solvents Dissolve Polar Solutes and Nonpolar Solvents Dissolve Nonpolar Solutes Practice
Using molecular polarity to predict solubility
Chemistry: Polar Solvents Dissolve Polar Solutes and Nonpolar Solvents Dissolve Nonpolar Solutes Practice
Using molecular polarity to predict solubility
Chemistry - Grade 9-12
- 1
Water is a polar solvent. Predict whether table salt, sodium chloride, will dissolve well in water. Explain your reasoning.
Ionic compounds usually behave like very polar solutes.
Sodium chloride will dissolve well in water because it is ionic, and ionic substances are strongly attracted to polar water molecules. The positive and negative ions can interact with the partial charges in water. - 2
Hexane is a nonpolar solvent. Predict whether vegetable oil, which is mostly nonpolar, will dissolve well in hexane. Explain your answer.
Vegetable oil will dissolve well in hexane because both substances are nonpolar. Nonpolar solutes are attracted to nonpolar solvents through London dispersion forces. - 3
A student mixes iodine, I2, with water and sees very little dissolving. Iodine is nonpolar. Explain why iodine does not dissolve well in water.
Compare the polarity of the solute and the solvent.
Iodine does not dissolve well in water because iodine is nonpolar while water is polar. The attractive forces between water molecules are not replaced well by attractions between water and iodine molecules. - 4
Ethanol has a polar O-H group and a short nonpolar carbon chain. It mixes completely with water. Explain why ethanol is soluble in water.
Ethanol is soluble in water because its polar O-H group can form hydrogen bonds with water molecules. Its short carbon chain is not large enough to prevent the polar part from interacting strongly with water. - 5
Carbon tetrachloride, CCl4, is a nonpolar solvent. Would potassium nitrate, KNO3, dissolve well in carbon tetrachloride? Explain your prediction.
A solvent must interact strongly with ions to dissolve an ionic compound.
Potassium nitrate would not dissolve well in carbon tetrachloride because potassium nitrate is ionic while carbon tetrachloride is nonpolar. A nonpolar solvent cannot strongly attract and separate the ions in the crystal. - 6
Rank these solutes from most likely to least likely to dissolve in water: methane, CH4; glucose, C6H12O6; sodium chloride, NaCl. Explain your ranking.
Sodium chloride and glucose are most likely to dissolve in water, while methane is least likely. Sodium chloride is ionic and interacts strongly with water, glucose is polar and can hydrogen bond with water, and methane is nonpolar. - 7
A nonpolar solvent is used to remove grease from a metal part. Grease is mostly made of long nonpolar hydrocarbon molecules. Explain why the nonpolar solvent is effective.
Use the phrase like dissolves like in your explanation.
The nonpolar solvent is effective because grease is mostly nonpolar. The nonpolar solvent molecules can mix with and attract the nonpolar grease molecules through dispersion forces, allowing the grease to dissolve. - 8
A student wants to dissolve sugar in two liquids: water and mineral oil. Sugar molecules contain many O-H groups and are polar. In which liquid should sugar dissolve better? Explain.
Sugar should dissolve better in water because both sugar and water are polar, and sugar can form hydrogen bonds with water. Mineral oil is nonpolar and cannot interact strongly with the polar sugar molecules. - 9
Benzene, C6H6, is nonpolar. Predict whether benzene will dissolve better in water or in hexane. Explain your answer.
Identify the solvent with polarity most similar to benzene.
Benzene will dissolve better in hexane because both benzene and hexane are nonpolar. Benzene will not dissolve well in water because water is polar and does not interact strongly with nonpolar benzene molecules. - 10
A compound has a polar end and a long nonpolar hydrocarbon tail. Predict whether it might act like soap. Explain how this structure helps it interact with both water and oil.
The compound might act like soap because its polar end can interact with polar water, while its nonpolar tail can interact with nonpolar oil or grease. This allows it to help mix or remove oily substances in water. - 11
Two liquids are mixed. Liquid A is polar, and liquid B is nonpolar. They form two separate layers instead of mixing. Explain why this happens.
Think about whether the attractions between unlike molecules are strong or weak.
The liquids form separate layers because polar and nonpolar molecules do not attract each other strongly enough to mix well. The polar molecules prefer to stay near other polar molecules, and the nonpolar molecules prefer to stay near other nonpolar molecules. - 12
A laboratory technician must choose a solvent to dissolve a polar unknown solid. The choices are water, hexane, and mineral oil. Which solvent is the best first choice, and why?
Water is the best first choice because it is polar and is most likely to dissolve a polar solid. Hexane and mineral oil are nonpolar, so they are less likely to dissolve the polar unknown well.